Starting switch and lockout device for electric discharge lamps



Feb. 29, 1944. 1 w. COOK STARTING SWITCH AND LOCK-OUT DEVICE FOR ELECTRIC DISCHARGE LAMPS Filed April 4, 1942 Fig.3.

Insulation 3 Insulation Inventor: Leonard W Cook,

y 7 His Attorney Feh. 2Q,

t -terrier? NiTt-E STARTING Sl/VITCH AND FLQCKQUT E'EVHQE FUR ELECTRIC DISCHARGE LAWS Leonard W. tlootk, Stratforrl, Conn, asslgnor to General Electric Company, a cornoration oi New York Application Anrii a,

Claims.

My invention relates to the starting of electric discharge lamps. Such lamps of a form in common use at the present time, for example i'luorescent lamps, are provided at opposite enrls with thermionic electrodes of filamentary form which prior to the starting of the discharge in the lamp have their temperatures raised to the point of electron emission by passing current through them in series with the ballasting means employed. When the temperature or" th electrodes has reached that point the circuit is interruptecl between them automatically by some form of switch whereby a surge of sufficient voltage is produced across the device to start the discharge. The electrodes of such lamps usually comprise a coil of refractory metal wire such tungsten coated with suitable electron emissive material such as an alkaline earth oxide and ar enclosed in a sealed envelope containing a rare or vapor, or both, in which the discharge takes place.

Not infrequently the discharge fails to start the first opening of the switch for, if at the instant of opening, the current is at or near the zero value of the wave, the applied voltage may he insufiicient to eiiect starting so a sec- 0nd or even a third attempt may required before a discharge in the lamp is started. In the event that the lamp is defective or has be come so in use and will not start clue, for example, to a loss of emission of its ectrorles or to contamination of its gaseous L. would result from a leak in the envelope, t switch will make repeated efforts to lamp. The repeated glowing oi the el the lamp in its unsuccessful so may soon become annoying to a ing the lamp; moreover, it this c lowed to continue, it may result destruction of the starting switch.

One object of my invention the r n of an improved starting switch v ing made a number of unsuccessiul to start a discharge in the lamp w th is used will automatically cease fur-ah tternpts.

Another object or" my invention is the provi= sion in combination with a lamp anti 1 switch therefor of a device which after th has made a number of successive unsuccess erupts to start the lamp will operate automati=- cally to deenergize the circuit of the starting switch and before the switch can again iunctlon as such will require the manual operation or means to effect the reenergization of switch. My invention will be better understood iron! the iollowing description taken in connection with the accompanying drawing, and its scope will be pointed out in the appended claims.

Referring to the drawing, Figs. 1

2. and 3 are cross sectional views of an embodiment of my invention showing the switch structure respectively in front, side and rear elevation; Fig. 4 is a circuit diagram; Figs. 5 and 6 are detail views of the starting switch as it appears under different operating conditions; anti Fig. 7 is a cletaii of the re-set button for the look-out device. In IEigs. i, 2 and. 3 the switch and iock=cut :ievice are shown mounted within the enclosing casing 51 preferably constructed of insulating material having the terminals 2 projecting from one end thereof by which the casing is adapted be secured in a suitable socket and the switch and lock-out device electrically connectecl with tlisoharse device. The open end of the cas ing is shown closetl the dish 3 which is he soruna into position. Snug-l fitting within 3S tron-averse plate of insuiatmaterial which serves to support the various el h and loclz out device. Se-

c one side thereof is the therzr which comprises the two pal l each 2 sec! or" a bimetallic stri The two s 32s are welded together at the point 9 with i 1'53 reverses" arranged respect to file whereby in response to an increase in tei ure the lower part 3 to the right, weel in Fig. the upper '3 warns to the r the ther a1 er is provi in the un all-=li2ze contact at? which of thermal morn" it with the contact circuit the heatesystem carri s nga ement with the front contact i5 circuit. The con which may be m 1 .ine small screw is secured to the strap it oy rivets to th plate 5. ion is threatled into the plate 2 the lower part 8 of the ther mal member enables one to adjust the initial tension the thermal member thereby detenmining the contact pressure between the contact iii anti the coonerating each contact ii. If the screw it is adjusted to produce but a slight ten V prefer to employ copper sion in the thl member and hence a very light initial pressure between the contacts iii and ii, the part 8 of the thermal member may be warped. sufficiently to make those contacts disengage after only a small amount of heat has been applied but that small heat impulse may not sufice to warp the thermal member far enough to'make the contact i engage the front contact produce a large initial tension in the thermal member and hence considerable pressure between the contacts l0 and l I, the thermal member even though heated to a much higher temperature than before still may not be able to move contact 90 into engagement with the contact is because of the great tension in the thermal memher. The adjustment of the screw it to select the proper tension of the thermal member therefore is critical between certain well defined limits.

Mounted on the opposite side of the plate by rivets is the look-out device which comprises the resilient member 20 which may be a small steel wire and the latch 2| therefor which, as shown, comprises a bimetallic strip whose upper end is bent at right angles to the body of the strip and is bevelled as shown in Fig. 2. When not heated, the bevelled end of the latch 2| is pressed against in Fig. 3. The latch 21 is arranged to be heated by the resistance heater 22, which may have a resistance of 30,000 ohms, and is thermally connected with the heater by the yoke 23 which preferably is constructed of copper. Since time delay is necessary in the action of the latch, I for the yoke because of its high specific heat and high conductivity. The yoke absorbs a large quantity of heat produced in the heater and later transmits the absorbed heat efficiently to the latch 2| without radiating it to other parts of the apparatus.

In response to being heated by the heater, the latch 2| warps away from the plate 4 to release the spring 20, the released position of the spring being indicated by dotted'lines. In order that 45 the spring may be re-set after it has been released and. without requiring the opening of the enclosing casing, I have provided the resetting button 25, the shank of which slides free- 1y larged base portionhas slots 26, see Fig. '7, formed therein which receive and are guided by parts of the plate 4 bordering a portion cut away to receive the button. The under side of the button has the bevelled slot 21 which receives 55 the bent upper end of the spring 20, the construction being such that when the spring is released by the latch 2|, its movement to the left, as seen in Fig. 3, pushes the button upward and when the button is pushed down by the finger of. a

person to re-set the look-out device, the spring 20 is forced to the right past the bevelled end of the latch 2| and is thereby retained in that position.

The circuit connections of the starting switch and lock-out device are more clearly shown in the circuit diagram comprising Fig. 4, where the discharge lamp 30 having electrodes 3|, the starting switch, and the lock-out device are shown connected to a source of alternating current supply 32, such, for example, as a 220-volt, 60-cycle lighting circuit through the ballast reactor 33.

The operation of the apparatus is as follows. When the apparatus the source of supply,

is initially connected'with a series circuit is closed the.

through theballast reactor 33, the electrode 3i at one end-of the lamp, the thermal member 8, contacts 60 and i l, the resistance heater i l, the bimetallic strip 2i, spring 20 and the other electrode 38, the heater 22 being subject to the potential difierence across the lamp. Because of the high resistance of the heater id, the voltage it. Moreover, if the screw is adjusted to applied to the heater 22 at this time is substantially that of the source, and the current which flows is not sufiicient to heat the lamp electrodes appreciably. Heat delivered to the part 8 of the thermal member from the heater it causes that part to warp tothe right and the contact it to disengage from the back contact H thereby opening the circuit of the heater. Because of the temperature head of the heater I4, heat continues to flow from the heater to the part 8 even after the circuit of the heater has been opened and by the resulting continued warping of the position being illustrated by Fig. 5. A low rethe plate 4 and thereby restrains the spring 20 in the circuit closing position shown through an opening in the disk 3 and the ensistancev path is thus closed between the two electrodes 3l and the resulting current flow quickly raises the temperature of the electrodes to the point of electron emission. .By the time they have reached that temperature or soon thereafter the part 8 will have cooled sufliciently to cause its contact I0 to separate from the front contact 16 and thus open the electrode heating circuit and, in the well known manner, apply a high inductive starting voltage to the lamp. The lamp presumably then starts. By reason of further cooling of the part 8 the contacts l0 and H reengage and the voltage applied to the heater [4 drops from a value which previously was substantially equal to that of the source to the value of the arc drop voltage of the lamp. Theheater with the latter voltage applied to it, however, is unable to supply suflicient heat to the thermal member to cause the contacts l0 and Hi again to engage to close the electrode heating circuit. Instead, the switch contact In floats between the front and rear contacts never touching the front contact l6 but intermittently touching the rear contact I l to which it returns as a result of cooling to re-energize the heater M. Because of the high resistance of the heater, the intermittent energization thereof by the engagement of contacts 10 and II produces no noticeable effect on the operation of the lamp.

Should the lamp have failed to start, the cooling of the thermal member will cause the contacts l0 and H to reengage each other, and because the voltage across the heater is then substantially that of the source the aforesaid operation of the starting switch will be repeated one or more times. Each time that the part 8 is heated in an attempt to start the lamp a certain amount of heat passes from the part 8 into the part I through the welded joint therebetween and as the temperature of the part 1 rises with continued starting attempts, it warps more and more to the'left. Finally after a number of unsuccessful attempts have been made'to start the lamp, which may be defective or may have become so with use, the part I will have become warped to the left to such an extent, as illustrated by Fig. 6, that the contact l0 willno longer disengage the back contact ll. Thus the switch will have automatically locked itself against closing the electrode heating circuit, in which condition the switch will remain until by the interruption of the current supply to the apparatus or by the replacement of the lamp, the

heater and the thermal member are allowed to cool. Inasmuch as the parts I and 8 comprising the thermal member 8 warp in opposite directions with a rise in temperature, the thermal member compensates for variations in temperature of the ambient since equal increases in temperature of both parts result in no appreciable movement of the contact ID.

If after the starting switch has automatically locked itself out in the manner described above because of its inability to start the lamp, the current supply is interrupted long enough for the heated parts of the switch to cool, the switch will again attempt to start the lamp when the supply voltage is restored. It has been found that with the switch so locked out, it may under certain other conditions make renewed attempts to start the lamp even though the supply voltage is not interrupted. For example, a drop in the voltage of the source of supply, a cold draft on the starting switch or a jar may be suilicient to upset the thermal balance of the switch system in its locked-out condition and cause a switch. The lamp continues to operate, but to extinguish it one needs only to interrupt the supply voltage for an instant. The lock out device having already opened the starting switch circuit, the lamp cannot restart.

What I claim as new and desire to secure by Letters Patent of the United States is:

i. In combination, a starting switch for an electric discharge lamp constructed alternately to insert high resistance between its terminals and to provide a short circuit therebetween, a lock-out switch biased to open circuit position connected in series with said starting switch, latching means for holding said lock-out switch closed, a high resistance heater connected across said starting switch and means responsive to a predetermined amount of accumulated heat received from said heater during a plurality of successive periods of high resistance between said momentary recycling of the switch. The functhat the switch shall not make any renewed eiiort to start the lamp due to causes such as a reduction in voltage, a cold draft on the switch. a jar or after the supply voltage has been reestablished after an interruption. Moreover, the look-out device requires a manual resetting to effect the re-energization of the starting switch. Since the resistance heater 22 of that device is connected across the lamp and as it comprises a high resistance it is responsive to the voltage across the lamp; hence, during those intervals when the starting switch contacts iii and i6 are not in engagement, the heater 22 is energized. This heater, the bimetallic latch 29, and the thermal connection therebetween are so constructed that after the starting switch has made a number of unsuccessful attempts to start thedevice and has ceased to make further attempts suflicient heat is received by the latch 2| from its heater 22. to cause it to release the spring 20 thus opening the circuit by which the switch is energized. It will be noted that whereas substantially the iull voltage of the source is applied to the heater 2! before the lamp starts except during those intervals when the contacts In and I8 are in engagement) after it starts, the voltage applied to the heater is only that of the Gil arc drop across the lamp. The latter voltage produces insumclent heat in heater 22 under normal lamp conditions to actuate the latch 2| even though applied continuously.

Many discharge lamps. particularly those which have nearly reached the ends of their useful lives, operate dimly and in a flickering manner since the arc discharge on each half cycle occurs well up on the voltage wave and the arc drop voltage is nearly equal to the no-load voltage supplied to the lamp. The starting switch may be able to start such a lamp but the continued operation thereof may be very annoying to those using the lamp. .A further function of the lockout device which I have provided is that with such a lamp operating the heat produced by the heater 22 will be great enough to release the latch 2|, thus opening the circuit of the starting terminals for releasing said latching means.

2. In combination, an electric discharge lamp having spaced electrodes adapted to be preheated by current flow therethrough, means for connecting one end of each of said electrodes with a source of current supply, a starting switch for said lamp connected between the other ends of said electrodes and constructed alternately to close and open until the lamp starts, a heater responsive to the voltage between said other ends of the electrodes, and a thermal switch arranged to interrupt the connection between said starting switch and said lamp in response to heat received from said heater and accumulated during a plurality of unsuccessful operations of said starting switch, the heat of said heater being insumcient under normal lamp conditions to open said thermal switch after the lamp starts.

3. In combination, an electric discharge lamp having spaced electrodes adapted to be preheated by current flow therethrough, means for connecting one end or each of said electrodes with a source of current supply, a starting switch for said lamp connected between the other ends of said electrodes and constructed alternately to short-circuit said lamp through its electrodes and to insert a high resistance in series therewith until the lamp starts, a resistance heater responsive to the voltage across said starting switch, and a switch arranged to interrupt the connection between said starting switch and said lamp, said switchv being biased to open circuit position and provided with a latch to retain it in closed circuit position, said latch being released in response to heat received from said heater and accumulated during a plurality of the successive intervals at which a high resistance is inserted between the electrodes, the voltage applied to the heater after the lamp starts being insumcient under normal lamp conditions to cause a. release of said latch.

4. In combination, a. starting switch for an electric discharge lamp constructed to undergo successive cycles alternately inserting high reslstance between its terminals and producing a short circuit therebetween. the periods of high resistance predominating over the periods of short circuit, a lock-out switch biased to open circuit position connected in series with said starting switch, a high resistance heater connected across said starting switch and latching means constructed to release said lock-out switch in re sponse to a predetermined amount of accumu lated heat from said heater.

. LEONARD W. COOK. 

